Process of preparing stable fatty monoglycerides



Oct. 27, 1959 J. G. BALDINUS 2,910,491

PROCESS OF PREPARING STABLE FATTY MONOGLYCERIDES Filed Feb. 11, 1957 4. 59 A I A Jose/w GEORGE Bum/v05 United States Patent PROCESS or PREPARING STABLE FATTY MONOGLYCERIDES Application February 11, 1957, Serial No. 639,582

7 Claims. (Cl. 260-410.7)

This invention relates to a process for producing stable fatty monoglycerides and more particularly to a process for producing the stable polymorphic form of a solid fatty monoglyceride.

Certain solid fatty monoglycerides are known to exhibit polymorphism, that is to exist in a plurality of solid states characterized by different crystal space lattices. Such monoglycerides may exist in the solid state as one polymorph or another, as an amorphous, non-crystalline material, or as mixtures of polymorphs alone or in admixture with amorphous material. However, there is only one space lattice configuration. comprising the thermodynamically stable solid state and any other solid state, either amorphous or crystalline, tends to convert either directly or indirectly to the stable polymorph.

This property of fatty monoglycerides is indicated by the fact that they normally freeze out of a melt in a low melting polymorphic form which on aging at room temperature gradually changes spontaneously to the high melting stable polymorph.

The state of the space lattice, in the case of crystalline fatty monoglycerides, may conveniently be studied by X-ray diffraction procedures, Figure 1 and Figure 2 being representative of typical X-ray diffraction patterns ob tained from such materials using copper K-alpha radiation filtered through a nickel foil and a camera 114.59 millimeters in diameter. Figure 1 representing a typical stable polymorph is characterized by the presence of two broad diffraction rings corresponding to interplanar distances of about 4.59 A. and 3.92 A. and a weak ring corresponding to 4.35 A. Figure 2 is typical of the unstable fatty monoglyceride polymorph which is prevalent at room temperatures, it being common for fatty monoglycerides to solidify in another unstable polymorphic configuration which on being cooled converts to the unstable configuration typically represented by Figure 2. Figure 2 may be characterized by a broad diffraction ring corresponding to an interplanar distance of about 4.13 A.

In the event that a fatty monoglyceride first solidifies as an amorphous non-crystalline solid, it normally quickly converts spontaneously to a crystalline structure.

It is common to use fatty monoglycerides as stabilizers in many different applications. It has been found that for certain purposes, such as the preparation of emulsified cosmetic creams and pastes, it is desirableto use the stable polymorphic form of a solid fatty monoglyceride in preference to an unstable polymorph. This is so because creams and pastes made with an unstable polymorph are frequently very thin and of unsatisfactorily low viscosity as compared to the same product when formulated with the stable form.

Prior to the present invention, in order to obtain the stable polymorph it was necessary to age unstable fatty monoglycerides until substantially complete spontaneous transformation had occurred, the period of aging depend ing upon the aging temperature and the particular composition involved. This is an unsatisfactory procedure Patented Oct. 27, 1959 involving, in some cases, time consuming operations and storage of relatively large inventories.

In accordance with the process of the present invention, an unstable form of a solid polymorphic fatty monoglyceride of a saturated fatty acid containing more than 12 carbon atoms is subjected to mechanical working sufficient to bring about a solid-solid transition to the stable polymorphic form. Such mechanical working is preferably performedpat a temperature approaching the melting point ofthe composition being processed.

The mechanical working required by the present invention contemplates subjecting an unstable fatty monoglyceride polymorph to a mechanical process of extrusion, compression, mastication, kneading, milling or other treatment which subjects a solid Working material to physically distortive forces. It is generally preferred to use a working process such as extrusion which facilitates control of the temperature of the material being worked. The working process should be carried out so as to effect substantially complete conversion to the stable form. For example, the working process should be conducted so that the content of unstable material is less than 10% and preferably less than 5% of the fatty acid monoglyceride present.

In the practice of the present invention the efficiency of mechanical working in effecting a phase transformation from an unstable solid form to the stable polymorph is a function of temperature, the process increasing in elficiency as the temperature of the material being worked rises up to just short of the melting point. A preferred embodiment of the present invention comprises mechanically working an unstable fatty monoglyceride polymorph at a temperature approaching its melting point since such an operation affords a maximum conversion with a minimum of working.

The present invention is particularly applicable to the unstable polymorphic monoglycerides derived from the saturated long chain fatty acids containing more than about 12 carbon atoms such as myristic, palmitic and stearic acids and mixtures thereof. Such monoglycerides frequently occur in an unstable polymorphic state under normal room conditions and require considerable aging before spontaneously converting substantially completely to the stable state, whereas the monoglycerides derived rom saturated fatty acids of 12 or less carbon atoms generally spontaneously convert substantially completely to the stable state at room temperature virtually instantaneously and therefore are seldom found in the unstable state. It is to be understood however, that the invention is not limited to the three specific fatty monoglycerides referred to above but is also applicable to other lung-chain solid fatty acid monoglycerides which are polymorphic in nature.

Although the present invention is applicable to pure or commercial fatty monoglycerides per se, it is also applicable to compositions containing substantial amounts of polymorphic fatty monoglycerides such as from about 20 to The invention is not applicable to foodstuffs, e.g. shortening, and cosmetic compositions wherein fatty monoglycerides are commonly used in amounts of the order of a few percent maximum, depending on the type of composition.

The following examples will serve as an illustration of a preferred embodiment of the present invention, but it is to be understood that the invention is not limited thereto.

Commercial glyceryl monostearate is prepared by heating commercial stearic acid (which contains about equal parts of stearic and palmitic acids and a minor amount of oleic acid) with glycerin in equimolar proportions at a temperature of about 250 C. for 2 /2 to 3 hours. The product, a mixture comprising approximately equal parts of glycerin, free fatty acids, water and triglycerides, is cooled to room temperature.

The melting point of such a composition is about 56- 57 C. and it exhibits an X-ray diffraction pattern similar to that of Figure 2.' Normally about 4 months aging at room temperature is necessary for substantially complete conversion to the stable phase to occur.

The freshly prepared material is subjected to 10 extrusions at 52 C. through a small extruding machine of the type customarily used for the extrusion of soap. After such extrusion, the composition is substantially completely in the stable phase as represented by the X-ray diffraction pattern of Figure 1.

A portion of the same composition when similarly worked at only 40 C. requires 25 extrusions to bring about substantially complete conversion to the stable state.

As indicative of the specificity of the present process, a commercial lard shortening was melted, cooled to room temperature, and subjected to 52 extrusions as described above. Analyses by X-ray diffraction showed that there was no change in the polymorphic state of the lard.

The preferred embodiment has described a solid-solid transformation starting with fatty monoglyceride in the solid state at room temperature, however, it is to be understood that it is within the ambit of the invention to take a molten or liquid monoglyceride, freeze or solidify it, and thereafter work or agitate the solidified product sufficiently to bring about a substantially complete solid transition to the stable polymorphic form. All of these steps may be carried out in a single piece of apparatus as a unitary batch or continuous operation.

Although the present invention has been described with reference to particular embodiments and examples, it will be apparent to those skilled in the art that variations and modifications can be substituted therefor without departing from the principles and true spirit of the invention.

This application is a continuation-in-part of application Serial No. 398,505, filed December 16, 1953.

Having thus described the invention, what is claimed is:

1. A process comprising subjecting an unstable form of a solid polymorphic monoglyceride of a saturated fatty acid containing more than 12 carbon atoms to mechanical working suflicient to bring about a substantially complete solid-solid transition to the thermodynamically normally stable polymorphic form.

2. A process as set forth in claim 1 in which said unstable fatty monoglyceride is glyceryl monopalmitate.

3. A process as set forth in claim 1 in which said unstable fatty monoglyceride is glyceryl monostearate.

4. A process which comprises subjecting a mixture of glyceryl esters containiug at least 20% of a normally unstable polymorphic form of a solid monoglyceride derived from a saturated fatty acid containing more than 12 carbon atoms to mechanical compressing and deforming forces sufficient to substantially completely transform said unstable monoglyceride to the thermodynamically normally stable solid state.

5. A process comprising subjecting a mixture of about equal parts of monopalmitin and monostearin which are in an unstable polymorphic configuration to sufficient mechanical working to bring about a substantially complete solid-solid transformation to the thermodynamically normally stable polymorphic form.

6. A process comprising subjecting an unstable form of a solid polymorphic monoglyceride of a saturated fatty acid containing more than 12 carbon atoms to sufficient extruding action to bring about a solid-solid transformation to the thermodynamically normally stable polymorphic form.

7. A process comprising subjecting an unstable form of a solid polymorphic monoglyceride of a saturated fatty acid containing more than 12 carbon atoms to mechanical working suflicient to bring about a solid-solid transition to the thermodynamically normally stable polymorphic form, said mechanical working being carried out at a temperature slightly below the. melting point of said monoglyceride.

References Cited in the file of this patent UNITED STATES PATENTS 2,557,135 Nelson June 19, 1951 2,625,483 Mattil et al Jan. 13, 1953 2,638,475 Ross May 12, 1953 2,815,286 Andre et al Dec. 3, 1957 OTHER REFERENCES Lutton: Journal American Oil Chemists Society, July 1950, vol. XXVII, No. 7, pages 276-281.

Bailey: Industrial Oil and Fat Products, 1951, page 218. 

1. A PROCESS COMPRISING SUBJECTING AN UNSTABLE FORM OF A SOLID POLYMORPHIC MONOGLYCERIDE OF A SATURATED FATTY ACID CONTAINING MORE THEN 12 CARBON ATOMS TO MECHANICAL WORKING SUFFICIENT TO BRING ABOUT A SUBSTANTIALLY COMPLETE SOLID-SOLID TRANSITION TO THE THERMODYNAMICALLY NORMALLY STABLE POLYMORPHIC FORM. 